In the typical screen printing processes, a screen having a pattern thereon is applied to a work product, dye or ink is placed on the screen, and the dye is urged through the screen to the surface of the work product by wiping the dye against the screen with a squeegee, etc. While screen printing has been used for many years in printing constant designs, considerable inconvenience is encountered when the pattern to be printed is to be changed. The screens are usually individually mounted or supported on the work product, so that when a new design is to be applied by the worker, the screen previously used must be set aside and another screen selected and used in the process. In situations where it is desirable to number or letter work products in sequence, the worker must change the individual number or letter screen on each cycle of printing, and a large supply of letters or numbers must be maintained at hand and handled for use in the process. When a variable screen printing process must be used at different locations, the several letter and number screens, the squeegee and other equipment must be collected and transported to the location where the process is to be performed. The letter and number screens are subject to being lost, damaged or becoming out of sequential order, and the worker may find it difficult to handle all of the elements of the system in some locations.